The usual method of thermal transfer recording is to employ a thermal transfer recording medium having a thermally fusible ink layer which is made by dispersing a coloring material in fusible substance on the supporting sheet and to heat the medium from the supporter side with a thermal head in the state superposing the ink layer on a receiving medium (usually a sheet of paper) and to transfer the melted ink layer on the receiving medium resulting to figure an ink image responding to heated portions.
This transfer-type thermal recording method has, however, a short point that the readability is not good because of the high lusterness of the obtained image.
Some ideas are proposed to remove this lusterness of printed image such as that, for example, the formation of irregularity on the surface of the thermally fusible colorant layer (that is, the surface of printed image) transferred on an image receiving layer by coating the thermally fusible colorant layer on a matted support (Japanese Patent Laid Open Publication No. 1985-212392) and the formation of irregularity on the surface of printed image by making a matt-layer or lusterness-control layer (both the layers are called "matt layer" hereafter) containing a resin and a delustering pigment on the base film and setting a thermally fusible colorant layer superposing on the matt-layer (Japanese Patent Laid Open Publication No. 1985-101083 and No. 1986-84287).
These thermal transfer recording medium produce a so-called void on the support corresponding the figure of transferred thermally fusible ink layer after the thermally fusible ink layer is transferred and the recorded content is made possible to read out. It proves the possibility of the leakage of secret.
Accordingly, consideration for secret preservation was utterly neglected in conventional type thermal transfer recording mediums. Since the irregularity formed on the surface of printed image is not satisfactorily fine, the removal of lusterness of the printed image is not complete. Readability is, therefore, not satisfactory depending on the angle of eyes.
Steady productivity could not be obtained for the manufacture of conventional type thermal transfer recording mediums because of the following reasons. In case of the thermal transfer recording medium having the irregularity on the support (refer to Japanese Patent Laid Open Publication No. 1985-2123929), the operation for irregularity treatment is complicated. In case of the thermal transfer medium having matt-layer (refer to Japanese Patent Laid Open Publication No. 1985-101083 and No. 1986-84287), the handling of an organic solvent for coating matt-layer is troublesome and unevenness of the coating layer is liable to cause.
It also left much room for improvement in quality of printing and the sensitivity.
The ink layer of thermal transfer recording mediums should be transferred exactly with a thermal head according to the state of each heated portion. That is to say, the ink layer of the thermal transfer recording medium should be peeled exactly from its support according to the state of heated portions. To satisfy this condition, a conventional technique has been used to apply a layer called a peelling layer between the support and the ink layer.
The peeling layer contains a thermally fusible substance such as wax as the main component and also contains a thermoplastic resin. This layer is applied on the support by coating components melted by heating or components dissolved or dispersed in an organic solvent.
For the purpose to obtain a good quality printed image it is desirable that the ink layer can be transferred from the support to the transferable medium with surface peeling which peels between peeling layer and the adjacent ink layer.
In case of the conventional peeling layers there has been troublesome problems such as surface peeling which occurs between the support and the adjacent peeling layer and the cohesive failure which occurs inside of the peeling layer. A desirable good printed image cannot be obtained if these phenomena happened.
Specially when the peeling layer is applied on the support by using an organic solvent there are many drawbacks such as the deterioration of the workplace environment, the necessity to equip a special fire-preventiven device or the increase of the production cost.